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Copyright © 3P Learning – These resources have been created in partnership with Dr. Marian Small.
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www.mathletics.comQuestions to facilitate the learning
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How many separate areas do you have to calculate to figure out the surface area?
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Could the dimensions have been whole numbers or did they have to be fractions or decimals?
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If you increase the length by 1 and width by 1, do you keep the same surface area or not?
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How do you know your results are correct?
Scaffolding the learning
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How many faces does the prism have? What do they look like?
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Why do some of the faces have to have the same dimensions? Do all of them?
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Suppose you made the height a big number. What does that mean about the length and width?
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Suppose you interchanged what you called the length and what you call the width. Would you have the
same prism with the same surface area or a different one?
Extending the learning
Students might use a triangular prism instead or the surface area could have been 30 cm
2
instead.
What’s the point of this task?
There are different strategies students can use to figure out the surface area of a rectangular prism.
Some might draw nets; others might visualise the faces in three dimensions. No matter how the problem
is approached, students will need to recognise that rectangular prisms have 3 pairs of congruent opposite
rectangular faces.
The total area selected was 75 square units, rather than 70 square units, for example, if students use
whole number dimensions the surface area is an even number, not an odd number. The use of 75
forces students to think about the phrase ‘close to’. Some students, no doubt, will use decimal or fractional
dimensions, though.
Although some students will use formulas for the area of a rectangle, students who are uncomfortable with
the formulas can use the grid background to help them.
Wrapping a Prism
Measurement